Detailed explanation of loop traversal and nesting usage of Python lists

1. List loop traversal

1.1 Use while to loop through the list

whileLoop allows us to access each element in the list one by one according to the criteria. usewhileWhen cycling, the loop variables and loop conditions need to be manually controlled.

Example：

names = ['Tom', 'Lily', 'Rose']
i = 0
while i < len(names):
    print(names[i])
    i += 1

In this example, we passwhileLooping through the listnames, and print out each name one by one.

1.2 Use for to loop through the list for

Loops provide a cleaner way to iterate through each element in a list without manually controlling the loop variables. Python'sforThe loop directly iterates the list.

Example：

names = ['Tom', 'Lily', 'Rose']
for name in names:
    print(name)

In this example, we useforLoop traversalnamesList, directly access each element and print it out. This method of code is simpler and easier to understand.

2. Nested use of lists

2.1 Creation of nested lists

Lists can contain other lists, thus forming a nested structure. This structure is very useful when processing grouped data, such as the list of students in the class.

Example：

classes = [
    ['Tom', 'Lily', 'Rose'],
    ['Alice', 'Bob', 'Charlie'],
    ['Jack', 'Mike', 'Lucy']
]

In this example,classesThe list contains three sublists, each of which represents a list of students in a class.

2.2 Accessing data from nested lists

Accessing data in nested lists requires layer by layer indexing. First, find the sublist through the outer index, and then access the specific data through the inner index.

Example：

classes = [
    ['Tom', 'Lily', 'Rose'],
    ['Alice', 'Bob', 'Charlie'],
    ['Jack', 'Mike', 'Lucy']
]
# Visit the second student in the second classprint(classes[1][1])  # Output: Bob

In this example, we first pass the outer index1Visit the student list of the second class and then pass the inner index1Find the studentBob。

3. Application scenarios of nested lists

Example：

students = [
    ['John', 'Sara', 'Mike'],
    ['Anna', 'Paul', 'Kate'],
    ['Tom', 'Lisa', 'Jake']
]
# Find specific studentstarget_student = 'Kate'
for group in students:
    if target_student in group:
        print(f"{target_student} In group {(group) + 1}")
        break

In this example, we traversestudentsEach sublist in the list, find the location of a specific student and output the results.

- **Storage grouped data**: Nested lists can be used to store data in multiple groups, such as student lists in multiple classes.
- **Organize Complex Data**: In data analysis and processing tasks, nested lists help organize and manage complex data structures.

4. Comprehensive application: randomly allocated offices

Suppose we have three offices and we need to randomly assign 8 teachers to these offices. This task can be achieved using a list.

4.1 Define data

Example：

import random

offices = [[], [], []]
teachers = ['Tom', 'Lily', 'Rose', 'Alice', 'Bob', 'Charlie', 'Jack', 'Mike']

4.2 Random assignment

Using PythonrandomModules can implement random assignment of tasks.

Example：

import random

offices = [[], [], []]
teachers = ['Tom', 'Lily', 'Rose', 'Alice', 'Bob', 'Charlie', 'Jack', 'Mike']

while teachers:
    teacher = (teachers)
    (teacher)
    office = (offices)
    (teacher)

print("Office Allocation Results:")
for i, office in enumerate(offices, 1):
    print(f"office {i}: {office}")

In this example, we randomly select teachers and offices through the () method to achieve random allocation.

5. Summary

The circular traversal and nested use of lists are important techniques in data processing. By mastering the use of while and for loops, we can effectively iterate through the data in the list. The nested use of lists can help us deal with complex data structures. In practical applications, these technologies can help us better organize and manage data, thereby improving programming efficiency and problem-solving capabilities.

The above is the detailed explanation of the loop traversal and nesting usage of Python lists. For more information about loop traversal and use of Python lists, please pay attention to my other related articles!